Sebelum dikenalnya portapak, belum ada teknologi yang menyerupai video camera. Kebanyakan teknologi dari tempat bekerja biasanya menggunakan tembakan pada jarak 16mm film, selain itu, siapa saja yang ingin mengabadikan semua kejadian dan kenang-kenangan dalam hidup mereka biasanya menggunakan 8 m/super 8 film.
Pada tahun 1967, Sony memperkenalkan portapak pertama, Sony DV-2400 video roker. “ portal I “video system. Merujuk pada lembaga elektronik, pada tahun 1982 antara JVC dan Sony memperkenalkan “ camerarecorder .” Pada tanggal 1 Juni 1982, camcorder JVC sudah menggunakan produk baru yakni VHS format yang berukuran kecil, VHS-C. Kemudian di Jepang 5 bulan kemudian, Sony memperkenalkan produk barunya yakni camcorder Betamovie, yang mana dipromosikan” dengan slogan “ Inside This Camera Is A VCR”. Camcorder Betamovie mendubrak pasar sekitar bulan Mei 1983, ini merupakan rekor pertama mesin tanpa menggunakan alat elektronik.
Sekarang ini camcorder merupakan evolusi terbaik dengan ciri-ciri mudah di bawa, simple, memiliki LCD yang lebar dan kualitas yang tinggi dalam pengambilan gambar dan bisa di bawa ke mana saja.
Video recording media
Betamax is the 1/2 inch (12.7 millimeter) home videocassette tape recording format introduced on April 16, 1975 (in market on May 10) and derived from the earlier, professional 3/4 inch (19.05 millimeter) U-matic video cassette format. Like the video home recording system VHS introduced by JVC in 1976, it had no guard band, and used azimuth recording to reduce cross-talk. The “Betamax” name came from a double meaning: beta being the Japanese word used to describe the way signals were recorded onto the tape, and from the fact that when the tape ran through the transport it looked like the Greek letter “Beta” (β). The suffix -max came from “maximum” to suggest greatness. Sanyo marketed a version as Betacord, but this was also referred to casually as “Beta.” In addition to Sony and Sanyo, Beta format video recorders were also sold by Toshiba, Pioneer, Aiwa and NEC, and the Zenith Electronics Corporation and WEGA Corporations contracted with Sony to produce VCRs for their product lines. Department stores like Sears, in the US and Canada, and Quelle in Germany sold Beta format VCRs under their house brands as did the RadioShack chain of electronic stores.
The legacy of Betamax
The VHS format’s defeat of the Betamax format became a classic marketing case study. Sony’s attempt to dictate an industry standard backfired when JVC made the tactical decision to forgo Sony’s offer of Betamax in favor of developing their own technology. They felt that it would end up like the U-Matic deal, with Sony dominating.
By 1980, JVC’s VHS format controlled 70% of the North American market. The large economy of scale allowed VHS units to be introduced to the European market at a far lower cost than the more-rare Betamax units. In the UK, Betamax held a 25% market share in 1981, but by 1986 it was down to 7.5% and continued to decline further. By 1984, forty companies utilized the VHS format in comparison with Beta’s twelve. Sony finally conceded defeat in 1988 when it too began producing VHS recorders.
In Japan, Betamax had more success and eventually evolved into Enhanced Definition Betamax with 500+ lines resolution, but eventually both Betamax and VHS were supplanted by laser-based technology. The last Sony Betamax was produced in 2002.
For more information on why Betamax lost to VHS, see The Videotape Format War. Home and professional recording
Sony produced a scaled-down version of Betamax for camcorders, and renamed it Video-8. The 8 mm cassette had the advantage with up to 4 hours length versus VHS-C’s 2 hour limit. On the down side, since the 8 mm format was incompatible with VHS, 8 mm recordings could not be played in home VCRs. Equally important entry-level VHS-C camcorders were priced less than 8 mm units, and thus neither “won” the war. It became a stalemate.
One other major consequence of the Betamax technology’s introduction to the U.S. was the lawsuit Sony Corp. v. Universal City Studios (1984, the “Betamax case”), with the U.S. Supreme Court determining home videotaping to be legal in the United States, wherein home videotape cassette recorders were a legal technology since they had substantial non-infringing uses. This precedent was later invoked in MGM v. Grokster (2005), where the high court agreed that the same “substantial non-infringing uses” standard applies to authors and vendors of peer-to-peer file sharing software (notably excepting those who “actively induce” copyright infringement through “purposeful, culpable expression and conduct”).
Three Sony Betamax VCRs built for the American market. Top to Bottom: (1982) SL-2000 portable with TT-2000 tuner/timer “Base Station”, (1984) SL-HF 300 Betamax HiFi unit, (1988) SL-HF 360 SuperBeta HiFi unit.
A rare Japanese market Betamax TV/VCR combo – Model SL-MV1.
The early form of Betacam tapes are interchangeable with Betamax, though the recordings are not.
In the professional and broadcast video industry, Sony’s Betacam, derived from Betamax as a professional format, became one of several standard formats; production houses exchange footage on Betacam videocassettes, and the Betacam system became the most widely used videotape format in the ENG (Electronic News Gathering) industry, replacing the 3/4″ U-matic tape format (which was the first practical and cost-effective portable videotape format for broadcast television, signaling the end of 16 mm film — and the phrase “film at 11” often heard on the six-o-clock newscast, before the film had been developed). The professional derivative of VHS, MII (aka Recam), faced off against Betacam and lost.
Once Betacam became the de facto standard of the broadcast industry, its position in the professional market mirrored VHS’s dominance in the home-video market. On a technical level, Betacam and Betamax are similar in that both share the same videocassette shape, use the same oxide tape formulation with the same coercivity, and both record linear audio tracks on the same location of the videotape. But in the key area of video recording, Betacam and Betamax are completely different. BetaCam tapes are mechanically interchangeable with Betamax, but not electronically. BetaCam moves the tape at 12 cm/sec, with different recording/encoding techniques. Betamax is a color-under system with linear tape speeds ranging from 4 cm/sec to 1.33 cm/sec.
Sony also offered a range of Industrial Betamax products, a Beta I only format for industrial and institutional users. Basically cheaper and smaller than U-Matic. The arrival of the Betacam system reduced the demand for both Industrial Beta and U-Matic equipment.
Betamax also had a significant part to play in the music recording industry when Sony introduced its PCM (Pulse Code Modulation) digital recording system as an encoding box / PCM adaptor that connected to a Betamax recorder. The Sony PCM-F1 adaptor was sold with a companion Betamax VCR SL-2000 as a portable digital audio recording system. Many recording engineers used this system in the 1980s and 1990s to make their first digital master recordings.
Initially, Sony was able to tout several Betamax-only features, such as BetaScan, a high speed picture search in either direction and BetaSkipScan, a technique that allowed the operator to see where he was on the tape by pressing the FF key (or REW, if in that mode) and the transport would switch into the BetaScan mode until the key was released. This feature is discussed more on Peep Search. Sony believed that the M-Load transports used by VHS machines made copying these trick modes impossible. BetaSkipScan (Peep Search) is now available on miniature M-load formats, but even Sony were unable to fully replicate this on VHS. BetaScan was originally called “Videola” until the company that made the Moviola threatened legal action.
Sony would also sell a BetaPak, a small deck designed to be used with a camera. Concerned with the need for several pieces, and cables to connect them, an integrated camera/recorder was designed, which Sony dubbed a “Camcorder”. The result was Betamovie. Betamovie used the standard sized cassette, but with a modified transport. The tape was wrapped 300 degrees around a smaller, 44.671 mm diameter head drum, with a single dual-azimuth head to write the video tracks. For playback, the tape would be inserted into a Beta format deck. Due to the different geometry and writing techniques employed, playback within the camcorder was not feasible. SuperBeta and Industrial Betamovie camcorders would also be sold by Sony.
Betamax introduced high fidelity audio to videotape, as Beta Hi-Fi. For NTSC, Betahifi worked by placing a pair of FM carriers between the chroma (C) and luminance (Y) carriers, a process known as audio frequency modulation. Each head had a specific pair of carriers, in total four individual channels were employed. Head A recorded its hifi carriers at 1.38(L) and 1.68(R) MHz, and the B head employed 1.53 and 1.83 MHz. The result was audio with an 80 dB dynamic range, with less than 0.005% wow and flutter.
Prior to the introduction of Beta Hi-Fi, Sony shifted the Y carrier up by 400 kHz to make room for the 4 FM carriers that would be needed for Beta Hi-Fi. All Beta machines incorporated this change, plus the ability to hunt for a lower frequency pre-AFM Y carrier. Sony incorporated an “anti-hunt” circuit, to stop the machine hunting for a Y carrier that wasn’t there.
Some Sony NTSC models were marketed as “Hi-Fi Ready” (with a SL-HFR prefix to the model’s number instead of the usual SL or SL-HF). These Betamax decks looked like a regular Betamax model, except for a special 28 pin connector on the rear. If the user desired a Beta Hi-Fi model but lacked the funds at the time, he could purchase an “SL-HFRxx” and at a later date purchase the separate Hi-Fi Processor. Sony offered two outboard Beta Hi-Fi processors, the HFP-100 and HFP-200. They were identical except that the HFP-200 was capable of multi-channel TV sound, with the word “stereocast” printed after the Beta Hi-Fi logo. This was possible because unlike a VHS Hi-Fi deck, an NTSC Betamax didn’t need an extra pair of heads. The HFP-x00 would generate the needed carriers which would be recorded by the attached deck, and during playback the AFM carriers would be passed to the HFP-x00. They also had a small “fine tracking” control on the rear panel for difficult tapes.
For PAL however, the bandwidth between the chroma and luminance carriers was not sufficient enough to allow additional FM carriers, so depth multiplexing was employed, where the audio track would be recorded in the same way that the video track was. The lower frequency audio track was written first by a dedicated head, and the video track recorded on top by the video head. The head disk had an extra pair of audio only heads with a different azimuth, positioned slightly ahead of the regular video heads, for this purpose.
Sony was confident that VHS could not achieve the same audio performance feat as Beta Hi-Fi. However, to the chagrin of Sony, JVC did develop a VHS hi-fi system on the principle of depth multiplexing approximately a year after the first Beta Hi-Fi VCR, the SL-5200, was introduced by Sony. Despite initial praise as providing “CD sound quality”, both Beta Hi-Fi and VHS HiFi suffered from “carrier buzz”, where high frequency information bled into the audio carriers, creating momentary “buzzing” and other audio flaws. Both systems also used companding noise-reduction systems, which could create “pumping” artifacts under some conditions. Both formats also suffered from interchange problems, where tapes made on one machine did not always play back well on other machines. When this happened, users were forced to revert to the old linear soundtrack.
In 1985 Sony would introduce a new feature, High Band or SuperBeta, by again shifting the Y carrier, this time by 800 kHz. This improved the bandwidth available to the Y sideband, and increased the horizontal resolution from 240 to 290 lines on a regular grade Betamax cassette. Since over-the-antenna and cable signals were only 300–330 lines resolution, SuperBeta could make a nearly-identical copy of live television. However, the chroma resolution still remained relatively poor, limited to just under 0.4 megahertz or approximately 30 lines resolution, whereas live broadcast chroma resolution was over 100 lines. The heads were also narrowed to 29 micrometres to reduce crosstalk, with a narrower head gap to play back the higher carrier frequency at 5.6 MHz. Later, some models would feature further improvement, in the form of Beta-Is, a high band version of the Beta-I recording mode. There were some incompatibilities between the older Beta decks and SuperBeta, but most could play back a high band tape without major problems. SuperBeta decks had a switch to disable the SuperBeta mode for compatibility purposes. (SuperBeta was only marginally supported, as many licensees had already discontinued their Betamax line.)
In 1988, Sony would again push the envelope with Beta ED or “Extended Definition” Betamax, capable of up to 500 lines of resolution, that equaled DVD quality (480 typical). In order to store the ~6.5 megahertz-wide luma signal, with the peak frequency at 9.3 MHz, Sony used a metal formulation tape from the Betacam (branded “ED-Metal”), and incorporated some improvements to the transport to reduce mechanically induced aberrations in the picture.Beta ED also featured a luminance carrier deviation of 2.5 MHz, as opposed to the 1.2 MHz used in SuperBeta, improving contrast with reduced luminance noise.
Sony introduced two ED decks and a camcorder in the late 1980s. The top end EDV-9300 deck was a very capable editing deck, rivalling much more expensive U-Matic setups for its accuracy and features, but did not have commercial success due to lack of timecode and other pro features. Sony did market Beta ED to “semi-professional” users, or “prosumers“. One complaint about the EDC-55 ED CAM was that it needed a lot of light (at least 25 lux), due to the use of two CCDs instead of the typical single CCD imaging device. The Beta ED lineup only recorded in BII/BIII modes, with the ability to play back BI/BIs.
Despite the sharp decline in sales of Betamax recorders in the late 1980s and subsequent halt in production of new recorders by Sony in 2002, both Betamax and SuperBetamax are still being used by a small number of people, most of whom are collectors or hobbyists. New cassettes are still available for purchase at online shops and used recorders are often found at flea markets, thrift stores, or on internet auction sites. Early format BetaCam cassettes, which are physically based on the Betamax cassette, continue to be available for use in the professional media.
Here is a list of modern-day, digital-type measurements (and traditional, analog horizontal resolutions in TV lines per picture height) for various media. The list only includes popular formats, not rare formats, and all values are approximate (rounded to the nearest 10), since the actual quality can vary machine-to-machine or display-to-display. For PAL media, replace 480 with 576. For ease of comparison all values are for the NTSC system, and listed in ascending order from lowest to highest quality.
- 350×240 (250 lines): Video CD
- 330×480 (250 lines): Umatic, Betamax, VHS, Video8
- 400×480 (300 lines): Super Betamax, Betacam (professional)
- 440×480 (330 lines): analog broadcast
- 560×480 (420 lines): LaserDisc, Super VHS, Hi8
- 670×480 (500 lines): Enhanced Definition Betamax
- 720×480 (500 lines): DVD, miniDV, Digital8, Digital Betacam (professional)
- 720×480 (400 lines): Widescreen DVD (anamorphic)
- 1280×720 (700 lines): D-VHS, HD DVD, Blu-ray, HDV (miniDV)
- 1920×1080 (1000 lines): D-VHS, HD DVD, Blu-ray, HDCAM SR (professional) Criticism
Size comparison between a Betamax cassette (top) and a VHS cassette (bottom).
A multitude of technical drawbacks hurt Betamax in its competition with VHS. The main issue with the format in the early days of the North American market was recording time. The original prototypes shown to Matsushita used a linear tape speed of 40 mm/sec. The technology of the day needed that speed due to the 60 micrometre heads employed. Management had also told engineering to deliver a cassette about the size of a paperback book. Sony engineers and management decided that since one hour was acceptable to the U-Matic’s buyers, it was acceptable for Betamax too, and made a small cassette practical. They would find that home buyers wanted longer run times than professional U-matic users.
When, in 1976, RCA introduced a VHS recorder capable of storing 4 hours on a standard T-120 tape, Americans and Canadians flocked to the longer run time, as it was perfect for recording the evening primetime schedule or afternoon football games. Sony immediately realized that 1 hour was not sufficient and introduced Beta-2 and Beta-3 speeds, but the smaller form factor limited maximum record time to only 5 hours due to the smaller cassette; roughly half the time that a VHS cassette could hold.
- Videotape format war
- Peep search – A picture search system pioneered with Betamax and available on most video formats since.
- Umatic – The predecessor to Betamax, using 19mm tape instead of ~12mm.
- Video8 – A small form factor tape based upon Betamax technology, using 8mm tape.
- Blu-ray Disc – Sony’s latest video tech.
A specially developed CCD used for ultraviolet imaging in a wire bonded package.
A charge-coupled device (CCD) is an analog shift register, enabling analog signals (electric charges) to be transported through successive stages (capacitors) controlled by a clock signal. Charge coupled devices can be used as a form of memory or for delaying analog, sampled signals. Today, they are most widely used for serializing parallel analog signals, namely in arrays of photoelectric light sensors. This use is so predominant that in common parlance, “CCD” is (erroneously) used as a synonym for a type of image sensor even though, strictly speaking, “CCD” refers solely to the way that the image signal is read out from the chip.
The capacitor perspective is reflective of the history of the development of the CCD and also is indicative of its general mode of operation, with respect to readout, but attempts aimed at optimization of present CCD designs and structures tend towards consideration of the photodiode as the fundamental collecting unit of the CCD. Under the control of an external circuit, each capacitor can transfer its electric charge to one or other of its neighbors. CCDs are used in digital photography and astronomy (particularly in photometry, sensors, medical fluoroscopy, optical and UV spectroscopy and high speed techniques such as lucky imaging).
The CCD was invented in 1969 by Willard Boyle and George E. Smith at AT&T Bell Labs. The lab was working on the picture phone and on the development of semiconductor bubble memory. Merging these two initiatives, Boyle and Smith conceived of the design of what they termed ‘Charge “Bubble” Devices’. The essence of the design was the ability to transfer charge along the surface of a semiconductor. As the CCD started its life as a memory device, one could only “inject” charge into the device at an input register. However, it was immediately clear that the CCD could receive charge via the photoelectric effect and electronic images could be created. By 1970, Bell researchers were able to capture images with simple linear devices; thus the CCD was born. Several companies, including Fairchild Semiconductor, RCA and Texas Instruments, picked up on the invention and began development programs. Fairchild was the first with commercial devices and by 1974 had a linear 500 element device and a 2-D 100 x 100 pixel device. Under the leadership of Kazuo Iwama, Sony also started a big development effort on CCDs involving a lot of money. Eventually, Sony managed to mass produce CCDs for their camcorders. Before this happened, Iwama died in August 1982. Subsequently, a CCD chip was placed on his tombstone to acknowledge his contribution..
In January 2006, Boyle and Smith were awarded the National Academy of Engineering Charles Stark Draper Prize for their work on the CCD.
An image is projected by a lens on the capacitor array, causing each capacitor to accumulate an electric charge proportional to the light intensity at that location. A one-dimensional array, used in line-scan cameras, captures a single slice of the image, while a two-dimensional array, used in video and still cameras, captures the whole image or a rectangular portion of it. Once the array has been exposed to the image, a control circuit causes each capacitor to transfer its contents to its neighbor. The last capacitor in the array dumps its charge into a charge amplifier, which converts the charge into a voltage. By repeating this process, the controlling circuit converts the entire semiconductor contents of the array to a sequence of voltages, which it samples, digitizes and stores in some form of memory. These stored images can then be transferred to a printer, digital storage device or video display.
“One-dimensional” CCD from a fax machine.
The photoelectric light sensor of a CCD is an isolated cable made of a semiconductor surrounded by ring electrodes. The low amount of free charge carriers, plus the finite polarization of the insulator and the semiconductor, only weakly disturb the electric field generated by the electrodes. Free carriers in the semiconductor cannot pass the insulator: they are said to be confined transversely. The ring-shaped electrodes are used to produce a sine-curve-shaped potential along the cable. Electrons drift to the potential hills, and holes drift to the valleys: they are said to be confined longitudinally. An alternating electric field on the electrodes makes the valleys and hills move along the cable, carrying the charge carriers with them.
Real CCDs are not round cables due to production issues. There are connections where charge carriers are injected. For readout, the small field disturbance generated by the carried charge is sensed (see: MOSFET). At the end of the cable, the carriers are dropped onto a metal electrode.
The photoactive region of the CCD is, generally, an epitaxial layer of silicon. It has a doping of p+ (Boron) and is grown upon the substrate material, often p++. In buried channel devices, the type of design utilized in most modern CCDs, certain areas of the surface of the silicon are ion implanted with phosphorus, giving them an n-doped designation. This region defines the channel in which the photogenerated charge packets will travel. The gate oxide, i.e. the capacitor dielectric, is grown on top of the epitaxial layer and substrate. Later on in the process polysilicon gates are deposited by chemical vapor deposition, patterned with photolithography, and etched in such a way that the separately phased gates lie perpendicular to the channels. The channels are further defined by utilization of the LOCOS process to produce the channel stop region. Channel stops are thermally grown oxides that serve to isolate the charge packets in one column from those in another. These channel stops are produced before the polysilicon gates are, as the LOCOS process utilizes a high temperature step that would destroy the gate material. The channels stops are parallel to, and exclusive of, the channel, or “charge carrying”, regions. Channel stops often have a p+ doped region underlying them, providing a further barrier to the electrons in the charge packets (this discussion of the physics of CCD devices assumes an electron transfer device, though hole transfer is possible).
One should note that the clocking of the gates, alternately high and low, will forward and reverse bias the diode that is provided by the buried channel (n-doped) and the epitaxial layer (p-doped). This will cause the CCD to deplete, near the p-n junction and will collect and move the charge packets beneath the gates – and within the channels – of the device.
It should be noted that CCD manufacturing and operation can be optimized for different uses. The above process describes a frame transfer CCD. While CCDs may be manufactured on a heavily doped p++ wafer it is also possible to manufacture a device inside p-wells that have been placed on an n-wafer. This second method, reportedly, reduces smear, dark current, and infrared and red response. This method of manufacture is used in the construction of interline transfer devices.
The CCD image sensors can be implemented in several different architectures. The most common are full-frame, frame-transfer and interline. The distinguishing characteristic of each of these architectures is their approach to the problem of shuttering.
In a full-frame device, all of the image area is active and there is no electronic shutter. A mechanical shutter must be added to this type of sensor or the image will smear as the device is clocked or read out.
With a frame transfer CCD, half of the silicon area is covered by an opaque mask (typically aluminium). The image can be quickly transferred from the image area to the opaque area or storage region with acceptable smear of a few percent. That image can then be read out slowly from the storage region while a new image is integrating or exposing in the active area. Frame-transfer devices typically do not require a mechanical shutter and were a common architecture for early solid-state broadcast cameras. The downside to the frame-transfer architecture is that it requires twice the silicon real estate of an equivalent full-frame device; hence, it costs roughly twice as much.
The interline architecture extends this concept one step further and masks every other column of the image sensor for storage. In this device, only one pixel shift has to occur to transfer from image area to storage area; thus, shutter times can be less than a microsecond and smear is essentially eliminated. The advantage is not free, however, as the imaging area is now covered by opaque strips dropping the fill factor to approximately 50% and the effective quantum efficiency by an equivalent amount. Modern designs have addressed this deleterious characteristic by adding microlenses on the surface of the device to direct light away from the opaque regions and on the active area. Microlenses can bring the fill factor back up to 90% or more depending on pixel size and the overall system’s optical design.
The choice of architecture comes down to one of utility. If the application cannot tolerate an expensive, failure prone, power hungry mechanical shutter, then an interline device is the right choice. Consumer snap-shot cameras have used interline devices. On the other hand, for those applications that require the best possible light collection and issues of money, power and time are less important, the full-frame device will be the right choice. Astronomers tend to prefer full-frame devices. The frame-transfer falls in between and was a common choice before the fill-factor issue of interline devices was addressed. Today, the choice of frame-transfer is usually made when an interline architecture is not available, such as in a back-illuminated device.
CCDs containing grids of pixels are used in digital cameras, optical scanners and video cameras as light-sensing devices. They commonly respond to 70% of the incident light (meaning a quantum efficiency of about 70%) making them far more efficient than photographic film, which captures only about 2% of the incident light.
Most common type of CCDs are sensitive to infrared light, which allows infrared photography, night-vision devices, and zero lux (or near zero lux) video-recording/photography. Because of their sensitivity to infrared, CCDs used in astronomy are usually cooled to liquid nitrogen temperatures, because infrared black body radiation is emitted from room-temperature sources. One other consequence of their sensitivity to infrared is that infrared from remote controls will often appear on CCD-based digital cameras or camcorders if they don’t have infrared blockers. Cooling also reduces the array’s dark current, improving the sensitivity of the CCD to low light intensities, even for ultraviolet and visible wavelengths.
Due to the high quantum efficiencies of CCDs, linearity of their outputs (one count for one photon of light), ease of use compared to photographic plates, and a variety of other reasons, CCDs were very rapidly adopted by astronomers for nearly all UV-to-infrared applications.
Thermal noise, dark current, and cosmic rays may alter the pixels in the CCD array. To counter such effects, astronomers take an average of several exposures with the CCD shutter closed and opened. The average of images taken with the shutter closed is necessary to lower the random noise. Once developed, the “dark frame” average image is then subtracted from the open-shutter image to remove the dark current and other systematic defects in the CCD (dead pixels, hot pixels, etc.). The Hubble Space Telescope, in particular, has a highly developed series of steps (“data reduction pipeline”) used to convert the raw CCD data to useful images. See  for a more in-depth description of the steps in processing astronomical CCD data.
CCD cameras used in astrophotography often require sturdy mounts to cope with vibrations and breezes, along with the tremendous weight of most imaging platforms. To take long exposures of galaxies and nebulae, many astronomers use a technique known as auto-guiding. Most autoguiders use a second CCD chip to monitor deviations during imaging. This chip can rapidly detect errors in tracking and command the mount’s motors to correct for them.
Array of 30 CCDs used on Sloan Digital Sky Survey telescope imaging camera, an example of “drift-scanning.”
An interesting unusual astronomical application of CCDs, called “drift-scanning”, is to use a CCD to make a fixed telescope behave like a tracking telescope and follow the motion of the sky. The charges in the CCD are transferred and read in a direction parallel to the motion of the sky, and at the same speed. In this way, the telescope can image a larger region of the sky than its normal field of view. The Sloan Digital Sky Survey is the most famous example of this, using the technique to produce the largest uniform survey of the sky yet.
A Bayer filter on a CCD
An RGBE filter on a CCD
Digital color cameras generally use a Bayer mask over the CCD. Each square of four pixels has one filtered red, one blue, and two green (the human eye is more sensitive to green than either red or blue). The result of this is that luminance information is collected at every pixel, but the color resolution is lower than the luminance resolution.
Better color separation can be reached by three-CCD devices (3CCD) and a dichroic beam splitter prism, that splits the image into red, green and blue components. Each of the three CCDs is arranged to respond to a particular color. Some semi-professional digital video camcorders (and most professionals) use this technique. Another advantage of 3CCD over a Bayer mask device is higher quantum efficiency (and therefore higher light sensitivity for a given aperture size). This is because in a 3CCD device most of the light entering the aperture is captured by a sensor, while a Bayer mask absorbs a high proportion (about 2/3) of the light falling on each CCD pixel.
Since a very-high-resolution CCD chip is very expensive as of 2005, a 3CCD high-resolution still camera would be beyond the price range even of many professional photographers. There are some high-end still cameras that use a rotating color filter to achieve both color-fidelity and high-resolution. These multi-shot cameras are rare and can only photograph objects that are not moving.
Sensors (CCD / CMOS) are often referred to with an imperial fraction designation such as 1/1.8″ or 2/3″, this measurement actually originates back in the 1950’s and the time of Vidicon tubes. Compact digital cameras and Digicams typically have much smaller sensors than a Digital SLR and are thus less sensitive to light and inherently more prone to noise. Some examples of the CCDs found in modern cameras can be found in this table in a Digital Photography Review article
A MiniDV Camcorder
Digital Video (DV) is a digital video format launched in 1996, and, in its smaller tape form factor MiniDV, has since become a standard for home and semi-professional video production; it is sometimes used for professional purposes as well, such as filmmaking and electronic news gathering (ENG). The DV specification (originally known as the Blue Book, current official name IEC 61834) defines both the codec and the tape format. Features include intraframe compression for uncomplicated editing, a standard interface for transfer to non-linear editing systems (IEEE 1394, also known as FireWire), and good video quality, especially compared to earlier consumer analog formats such as Video8, Hi8 and VHS-C. DV now enables filmmakers to produce movies inexpensively, and is strongly associated with independent film and citizen journalism.
The high quality of DV images, especially when compared to Video8 and Hi8, which were vulnerable to an unacceptable amount of video dropouts and “hits,” prompted the acceptance of material shot on DV to be accepted by mainstream broadcasters. The low costs of DV equipment and their ease of use put such cameras in the hands of a new breed of videojournalists. Programs such as TLC’s Trauma: Life in the E.R. and ABC News’ Hopkins: 24/7 were shot on DV. CNN’s Anderson Cooper is perhaps the best known of the generation of reporter/videographers who began their profession careers shooting their own stories.
There have been some variants on the DV standard, most notably Sony’s DVCAM and Panasonic’s DVCPRO formats targeted at professional use. Sony’s consumer Digital8 format is another variant, which is similar to DV but recorded on Hi8 tape. Other formats such as DVCPRO50 utilize DV25 encoders running in parallel.
MiniDV tapes can also be used to record a high-definition format called HDV in cameras designed for this codec, which differs significantly from DV on a technical level as it uses MPEG-2 compression. MPEG-2 is more efficient than the compression used in DV, in large part due to inter-frame/temporal compression. This allows for higher resolution at bitrates similar to DV. On the other hand, the use of inter-frame compression can cause motion artifacts and complications in editing. Nonetheless, HDV is being widely adopted for both consumer and professional purposes and is supported by many editing applications using either the native HDV format or intermediary editing codecs.
To avoid aliasing, optical low pass filtering is necessary (although not necessarily implemented in all camera designs). Essentially, blurry glass is used to add a small blur to the image. This prevents high-frequency information from getting through and causing aliasing. Low-quality lenses can also be considered a form of optical low pass filtering.
Before arriving at the codec compression stage, light energy hitting the sensor is transduced into analog electrical signals. These signals are then converted into digital signal by an analog to digital converter (ADC or A/D). This signal is then processed by a digital signal processor (DSP) or custom ASIC and undergoes the following processes:
Processing of raw input into (linear) RGB signals: For Bayer pattern-based sensors (i.e. sensors utilizing a single CCD or CMOS and color filters), the raw input has to be demosaiced. For Foveon-based designs, the signal has to be processed to remove cross-talk between the color layers. In pixel-shifted 3CCD designs, a process somewhat similar to de-mosaicing is applied to extract full resolution from the sensor.
Matrix (for colorimetry purposes): The digital values are matrixed to tweak the camera’s color response to improve color accuracy and to make the values appropriate for the target colorimetry (SMPTE C, Rec. 709, or EBU phosphor chromaticities). For performance reasons, this matrix may be applied after gamma correction and combined with the matrix that converts R’G’B’ to Y’CbCr.
Electronic white balance may be applied in this matrix, or in the matrix operation applied after gamma correction.
Gamma correction: Gamma correction is applied to the linear digital signal, following the Rec. 601 transfer function (a power function of 1/0.45). Note that this increases the quantization error from before.
Matrix (R’G’B’ to Y’CbCr conversion): This matrix converts the gamma-corrected R’G’B’ values to Y’CbCr color space. Y’CbCr color space facilitates chroma subsampling. This operation introduces yet more quantization error, in large part due to a difference in the scale factors between the Y’ and Cb and Cr components.
Chroma Subsampling: Since human vision has greater acuity for luminance than color, performance can be optimized by devoting greater bandwidth to luminance than color. Chroma subsampling approximates this by converting R’G’B’ values into Y’CbCr color space. The Cb and Cr color difference components are stored at a lower resolution than the Y’ (luma) component.
Sharpening is often used to counteract the effect of optical low pass filtering. Sharpening can be implemented via finite impulse response filters.
DV uses DCT intraframe compression at a fixed bitrate of 25 megabits per second (25.146 Mbit/s), which, when added to the sound data (1.536 Mbit/s), the subcode data, error detection, and error correction (approx 8.7 Mbit/s) amounts in all to roughly 36 megabits per second (approx 35.382 Mbit/s). At equal bitrates, DV performs somewhat better than the older MJPEG codec, and is comparable to intraframe MPEG-2. (Note that many MPEG-2 encoders for real-time acquisition applications only use intraframe compression [I-frames only], but not interframe compression [P and B frames].) DCT compression is lossy, and sometimes suffers from artifacting around small or complex objects such as text. The DCT compression has been specially adapted for storage onto tape. The image is divided into macroblocks, each consisting of 4 luminance DCT blocks and 1 chrominance DCT block. Furthermore 6 macroblocks, selected at positions far away from each other in the image, are coded into a fixed amount of bits. Finally, the information of each compressed macroblock is stored as much as possible into one sync-block on tape. All this makes it possible to search video on tape at high speeds, both forward and reverse, as well as to correct very well faulty sync blocks.
The chroma subsampling is 4:1:1 for NTSC, 4:1:1 for DVCPRO PAL, and 4:2:0 for other PAL. Not all analog formats are outperformed by DV. The Betacam SP format, for example, can still be desirable because it has slightly greater chroma fidelity and no digital artifacts.
Low chroma resolution is a reason why DV is sometimes avoided in applications where chroma-key will be used. Nevertheless, advances in keying software (i.e. the combination of chroma keying with different keying techniques, chroma interpolation) allows for reasonable quality keys from DV material.
DV allows either 2 digital audio channels (usually stereo) at 16 bit resolution and 48 kHz sampling rate, or 4 digital audio channels at 12 bit resolution and 32 kHz sampling rate. For professional or broadcast applications, 48 kHz is used almost exclusively. In addition, the DV spec includes the ability to record audio at 44.1 kHz (the same sampling rate used for CD audio), although in practice this option is rarely used. DVCAM and DVCPRO both use locked audio while standard DV does not. This means that at any one point on a DV tape the audio may be +/- ⅓ frame out of sync with the video. However, this is the maximum drift of the audio/video sync; it is not compounded throughout the recording. In DVCAM and DVCPRO recordings the audio sync is permanently linked to the video sync.
The FireWire (aka IEEE 1394) serial data transfer bus is not a part of the DV specification, but co-evolved with it. Nearly all DV cameras have an IEEE 1394 interface and analog composite video and Y/C outputs. High end DV VTRs may have additional professional outputs such as SDI, SDTI or analog component video. All DV variants have a timecode, but some older or consumer computer applications fail to take advantage of it. Some camcorders also feature a USB2 port for computer connection, but these are sometimes not capable of capturing the DV stream in full detail, and are instead used primarily for transferring certain digital data from the camcorder such as still pictures and computer-format video files (such as MPEG4-encoded video). This carries Audio Video and Control Signals.
Dvcassettes Left to right: DVCAM-L, DVCPRO-M, MiniDV
The DV format uses “L-size” cassettes, while MiniDV cassettes are called “S-size”. Both MiniDV and DV tapes can come with a low capacity embedded memory chip (MIC) (most commonly, a scant 4 Kbit for MiniDV cassettes, but the system supports up to 16 Kbit). This embedded memory can be used to quickly sample stills from edit points (for example, each time the record button on the camcorder is pressed when filming, a new “scene” timecode is entered into memory). DVCPRO has no “S-size”, but an additional “M-size” as well as an “XL-size” for use with DVCPRO HD VTRs. All DV variants use a tape that is ¼ inch (6.35 mm) wide.
The “L” cassette is about 120 × 90 × 12 mm and can record up to 4.6 hours of video (6.9 hours in EP/LP). The better known MiniDV “S” cassettes are 65 × 48 × 12 mm and hold either 60 or 90 minutes of video (13 GB) depending on whether the video is recorded at Standard Play (SP) or Extended Play (sometimes called Long Play) (EP/LP). 80 minute tapes that use thinner tape are also available and can record 120 minutes of video in EP/LP mode. The tapes sell for as little as US$3.00 each in quantity as of 2006. DV on SP has a helical scan track width of 10 micrometres, while EP uses a track width of only 6.7 micrometres. Since the tolerances are much tighter, the recorded tape may not play back properly or at all on other devices.
A disassembled MiniDV tape.
Software is currently available for ordinary home computers which allows users to record any sort of computer data on MiniDV cassettes using common DV decks or camcorders. Though originally intended for the consumer market as a high-quality replacement for VHS, L-size DV cassettes are largely nonexistent in the consumer market, and are generally used only in professional settings. Even in professional markets, most DV camcorders support only MiniDV, though many professional DV VTRs support both sizes of tape.
Sony’s DVCAM is a professional variant of the DV standard that uses the same cassettes as DV and MiniDV, but transports the tape 50% faster. This leads to a higher track width of 15 micrometres. This variant uses the same codec as regular DV. However, the greater track width lowers the chances of dropout errors. The LP mode of consumer DV is not supported. All DVCAM recorders and cameras can play back DV material, but DVCPRO support was only recently added to some models like DSR-1800, DSR-2000, DSR-1600. DVCAM tapes (or DV tapes recorded in DVCAM mode) have their recording time reduced by one third.
Because of wider track DVCAM has the ability to do a frame accurate insert tape edit. DV will vary by a few frames on each edit compared to the preview. Another feature of DVCAM is locked audio. If you make a copy of a copy of a copy of a copy on DV, the audio sync may drift a bit. On DVCam this does not happen.
Panasonic specifically created the DVCPRO family for electronic news gathering (ENG) use, with better linear editing capabilities and robustness. It has an even greater track width of 18 micrometres and uses another tape type (Metal Particle instead of Metal Evaporated). Additionally, the tape has a longitudinal analog audio cue track. Audio is only available in the 16 bit/48 kHz variant, there is no EP mode, and DVCPRO always uses 4:1:1 color subsampling (even in PAL mode). Apart from that, standard DVCPRO (also known as DVCPRO25) is otherwise identical to DV at a bitstream level. However, unlike Sony, Panasonic chose to promote its DV variant for professional high-end applications.
DVCPRO50 is often described as two DV-codecs in parallel. The DVCPRO50 standard doubles the coded video bitrate from 25 Mbit/s to 50 Mbit/s, and uses 4:2:2 chroma subsampling instead of 4:1:1. DVCPRO50 was created for high-value ENG compatibility. The higher datarate cuts recording time in half (compared to DVCPRO25), but the resulting picture quality is reputed to rival Digital Betacam.
DVCPRO HD, also known as DVCPRO100, uses four parallel codecs and a coded video bitrate of approximately 100 Mbit/s, depending on the format flavour. DVCPRO HD encodes using 4:2:2 color sampling. DVCPRO HD prefilters the 720p image from the DSP to a recorded size of 960×720, and 1080i is prefiltered to 1280×1080 for 59.94i and 1440×1080 for 50i. This is a common technique, utilized in most tape-based HD formats such as HDCam and HDV. The final DCT compression ratio is approximately 6.7:1. To maintain compatibility with HDSDI, DVCPRO100 equipment upsamples video during playback. A camcorder using a special variable-framerate (from 4 to 60 frame/s) variant of DVCPRO HD called VariCam is also available. All these variants are backward compatible but not forward compatible. There is also a DVCPRO HD EX format, which runs the tape at slower speed, resulting in twice as long recording times. DVCPRO-HD is codified as SMPTE 370M; the DVCPRO-HD tape format is SMPTE 371M, and the MXF Op-Atom format used for DVCPRO-HD on P2 cards is SMPTE 390M.
DVCPRO cassettes are always labeled with a pair of run times, the smaller of the two being the capacity for DVCPRO50. A “M” tape can hold up to 66/33 minutes of video. The color of the lid indicates the format: DVCPRO tapes have a yellow lid, longer “L” tapes made specially for DVCPRO50 have a blue lid and DVCPRO HD tapes have a red lid. The formulation of the tape is the same, and the tapes are interchangeable between formats. The running time of each tape is 1x for DVCPRO, 2x for DVCPRO 50, 2x for DVCPRO HD EX, and 4x for DVCPRO HD, since the tape speed changes between formats. Thus a tape made 126 minutes for DVCPRO will last approximately 32 minutes in DVCPRO HD.
Memory in cassette
Some MiniDV cassettes have a small memory chip referred to as memory in cassette (MIC). Cameras and recording decks can record any data desired onto this chip including a contents list, times and dates of recordings, and camera settings used. It is EEPROM memory using the I²C protocol. The members of the MIC range are available in two forms:
- The MIC-R family
The MIC-R family works with serial EEPROM capacities between 1 Kbit and 8 Kbit (the I²C-compatible EEPROM devices: M24C01, M24C02, M24C04 and M24C08).
- The MIC-S family
The MIC-S family works with serial EEPROM capacities greater or equal to 16 Kbit (the XI2C-compatible EEPROM devices: M24C16, M24C32 and M24C64).
Both families are compliant with the DV standard. For detailed information see datasheet: Serial I²C bus EEPROM (STMicroelectronics).
MIC functionality is not widely used on the consumer level; most tapes available to consumers do not even include the chip, which adds substantially to the price of each cassette. Most consumer equipment includes the circuitry to read and write to the chip even though it is rarely used.
Digital video dates back to 1986, with the creation of the uncompressed D-1 format for professional use (although several professional video manufacturers such as Sony, Ampex, RCA, and Bosch had experimentally developed prototype digital video recorders dating back to the mid-to-late 1970s).
Sony has several digital specifications for professional use, the most common for standard definition use being Digital Betacam, a distant descendant of the Betamax products of the 1970s thru 1990s from which it received only some mechanical aspects, notably the form of the cassette. (Betamax itself descended from Sony’s U-Matic ¾ inch videocassette system.)
JVC‘s D-9 format (also known as Digital-S) is very similar to DVCPRO50, but records on videocassettes in the S-VHS form factor. (NOTE: D-9 is not to be confused with D-VHS, which uses MPEG-2 compression at a significantly lower bitrate.)
The Digital8 standard uses the DV codec, but replaces the recording medium with the older Hi8 videocassette. Digital8 theoretically offers DV’s digital quality, without sacrificing playback of existing analog Video8/Hi8 recordings. However, in practice the maximum quality of the format is unlikely to be achieved, since Digital8 is largely confined to low-end consumer camcorders. It is also a semi-proprietary format, being manufactured exclusively by Sony (although Hitachi also made Digital8 camcorders briefly).
DVD was originally created as a distribution format, but recordable DVDs quickly became available. Camcorders using miniDVD media are fairly common on the consumer level, but due to difficulties with editing the MPEG-2 data stream, they are not widely used in professional settings.
Sony also made a format called MicroMV, which stored MPEG-2 video on a matchbox-sized tape. Due to lack of platform support and the difficulties of editing MPEG-2 video, MicroMV never became popular and was discontinued by 2005.
Sony’s XDCAM format allows recording of MPEG IMX, DVCAM and low resolution streams in an MXF wrapper on a Sony ProDATA disc, an optical medium similar to a Blu-ray Disc. Sony has also, in cooperation with Panasonic, created AVCHD, a medium-independent codec for consumer high definition video; it is currently used on camcorders containing hard disks and DVD-R drives for storage.
Most DV players, editors and encoders only support the basic DV format, but not its professional versions. DV Audio/Video data can be stored as raw DV data stream file (data is written to a file as the data is received over FireWire, file extensions are .dv and .dif) with all DV meta-information preserved or the DV data can be packed into AVI container files (this only preserves audio and video, not meta data).
- The Apple Inc.‘s QuickTime Player: QuickTime by default only decodes DV to half of the resolution to preserve processing power for editing capabilities. However, in the “Pro” version the setting “High Quality” under “Show Movie Properties” enables full resolution playback.
- DVMP Basic & DVMP Pro: full decoding quality. Plays AVI (inc DVCPRO25 and DVCAM) and .dv files. Also displays the DV meta-information (e.g. timecode, date/time, f-stop, shutter speed, gain, white balance etc)
- The VLC media player (Free software): full decoding quality
- MPlayer (also with GUI under Windows): full decoding quality
- muvee Technologies autoProducer 4.0: Allows editing using FireWire IEEE 1394
- Quasar DV codec (libdv) – open source DV codec for Linux
Type 1 and Type 2 DV AVI files
There are two types of DV-AVI files:
- Type 1: The multiplexed Audio-Video is kept in its original multiplexing and saved together into the Video section of the AVI file
- Type 2: Like type 1, but audio is also saved as an additional audio stream into the file.
- Supported by VfW applications, at the price of little increased file size.
Type 1 is actually the newer of the two types. Microsoft made the “type” designations, and decided to name their older VfW-compatible version “Type 2”, which only furthered confusion about the two types. In the late 1990s through early 2000s, most professional-level DV software, including non-linear editing programs, only supported Type 1. One notable exception was Adobe Premiere, which only supported Type 2. High-end FireWire controllers usually captured to Type 1 only, while “consumer” level controllers usually captured to Type 2 only. Software is and was available for converting Type 1 AVIs to Type 2, and vice-versa, but this is a time-consuming process.
Many current FireWire controllers still only capture to one or the other type. However, almost all current DV software supports both Type 1 and Type 2 editing and rendering, including Adobe Premiere. Thus, many of today’s users are unaware of the fact that there are two types of DV AVI files. In any event, the debate continues as to which – Type 1 or Type 2 – if either, is better.
There is controversy over whether or not using tapes from different manufacturers can lead to dropouts. The problem theoretically occurs when incompatible lubricants on tapes of different types combine to become tacky and deposit on tape heads. This problem was supposedly fixed in 1997 when manufacturers reformulated their lubricants, but users still report problems several years later. Much of the evidence relating to this issue is anecdotal or hearsay. In one case, a representative of a manufacturer (unintentionally) provided incorrect information about their tape products, stating that one of their tape lines used “wet” lubricant instead of “dry” lubricant. The issue is complicated by OEM arrangements: a single manufacturer may make tape for several different brands, and a brand may switch manufacturers.
8 mm video format
The 8 mm video format refers informally to three related videocassette formats for the NTSC and PAL/SECAM television systems. These are the original Video8 format and its improved successor Hi8 (both analog), as well as a more recent digital format known as Digital8.
Their user-base consisted mainly of amateur camcorder users, although they also saw important use in the professional field.
The format was introduced in 1985, the year that Sony of Japan introduced the Handycam, one of the first Video8 cameras. Much smaller than the competition’s VHS and Betamax video cameras, Video8 became very popular in the consumer camcorder market.
The three formats (Video8, Hi8 and Digital8) are physically very similar, featuring both the same tape-width and near-identical cassette-shells measuring 95 x 62.5 x 15 mm. This gives a measure of backward-compatibility in some cases. One difference between them is in the quality of the tape itself, but the main differences lie in the encoding of the video when it is recorded onto the tape.
Video8 was the earliest of the three formats, and is entirely analog. The 8 mm tape width was chosen as smaller successor to the 12mm Betamax format, using similar technology (including U-shaped tape loading), but in a smaller form factor and in response to the small form factor VHS-C compact camcorders introduced by the competition. It was followed by a version with improved resolution, Hi8. Although this was still analog, some professional Hi8 equipment could store additional digital-stereo PCM sound on a special reserved track.
Digital8 is the most recent 8 mm video format. It retains the same physical cassette shell as its predecessors, and can even record onto Video 8 (not recommended) or Hi8 cassettes. However, the format in which video is encoded and stored on the tape itself is the entirely digital DV format (and thus very different from the analog Video8 and Hi8). Some Digital8 camcorders support Video8 and Hi8 with analog sound (for playback only), but this is not required by the Digital8 specification.
In all three cases, a length of 8 mm-wide magnetic tape is wound between two spools and held within a hard-shelled cassette. These cassettes share similar size and appearance with the audio cassette, but their mechanical operation is far closer to that of VHS or Betamax videocassettes. Standard recording time is up to 180 minutes for PAL and 120 minutes for NTSC. (The cassette holds the same length tape – tape-consumption is different between PAL and NTSC recorders.)
Like most other videocassette systems, Video8 uses a helical-scan head-drum to read/write video to the magnetic tape. The drum rotates at high speed (one or two rotations per picture frame – about 1800 or 3600 rpm for NTSC, and 1500 or 3000 rpm for PAL) while the tape is pulled along the drum’s path. Because the tape and drum are oriented at a slight angular offset, the recording tracks are laid down as parallel diagonal stripes on the tape.
An amateur grade Video8 Camcorder from the early 1990s.
Video8 was launched into a market dominated by the VHS-C and Betamax formats.
In 1983 Sony Betamax had released the first camcorder called Betamovie. In response JVC released the compact VHS-C format which enabled the first handheld (rather than shoulder-mounted) camcorders. Sony’s answer to these small cameras came in 1985 when they used Betamax-style U-load technology, but reduced the tape width from 12 millimeter to 8 millimeter, and the Video8 format was born.
In terms of video quality, Video8, VHS/VHS-C, and Beta-II offered similar performance in their “standard play” modes; all were rated at approximately 240 horizontal lines (depending on speed, quality of tape, and other factors). In terms of audio, Video8 generally outperformed its older rivals. Standard VHS and Beta audio was recorded along a narrow linear track at the edge of the tape, where it was vulnerable to damage. Coupled with the slow horizontal tape speed, the sound was comparable with that of a low-quality audio cassette. By contrast, all Video8 machines used “audio frequency modulation” (AFM) to record sound along the same helical tape-path as that of the video signal. This meant that Video8’s standard audio was of a far higher quality than that of its rivals, although linear audio did have the advantage that (unlike either AFM system), it could be re-recorded without disturbing the underlying video. (Betamax and VHS Hi-Fi rarely appeared on camcorders, except on the high-end models.) Video8 later included true stereo, but the limitations of camcorder microphones at the time meant that there was little practical difference between the two AFM systems for camcorder usage. In general, Video8 comfortably outperformed non-HiFi VHS/Beta.
Video8 had one major advantage over the full-sized competition. Thanks to their compact-form factor, Video8 camcorders were small enough to hold in the palm of the user’s hand. Such a feat was impossible with Betamax and VHS camcorders, which operated best on sturdy tripods or strong shoulders. Video8 also had an advantage in terms of time, because although VHS-C offered the same “palmcorder” size as Video8, the VHS-C tapes only held 40 minutes of time (SP). Thus Video8’s 120-minute capacity served well for most users. (Both machines included longer playing modes at 120 and 240 minutes respectively, but at the cost of reduced quality images of only 220 lines resolution.) Longer sessions generally required additional infrastructure (AC power or more batteries), and hence longer recording-times offered little advantage in a true travelling environment.
Video8/Hi8’s main drawback was that tapes made with Video8 camcorders could not be played directly on VHS hardware. Although it was possible to transfer tapes (using the VCR to re-record the source video as it was played back by the camcorder), this inevitably led to degradation of the analog signal.
Ultimately, Video8’s main rival in the camcorder market turned out to be VHS-C, with neither dominating the market completely. However, both formats (along with their improved descendants, Hi8 and SVHS-C) were nevertheless very successful. Collectively, they dominated the camcorder market for almost two decades before they were eventually crowded out by digital formats such as MiniDV and DVD recordable.
To counter the introduction of the Super-VHS format, Sony introduced Video Hi8 (short for high-band Video8.) Like SVHS, Hi8 used improved recorder electronics and media-formulation to increase picture detail. In both systems, a higher-grade videotape and recording-heads allowed the placement of the luminance-carrier at a higher frequency, thereby increasing luminance bandwidth. Both Hi8 and SVHS were officially rated at a luminance resolution of 420 horizontal TV/lines (560×480 in today’s digital terms), a vast improvement from their respective base-formats of 240 lines and roughly equal to laserdisc quality. Chroma resolution for both remained unchanged at approximately 30 lines horizontal. All Hi8 equipment supported recording and playback of both Hi8 and legacy Video8 recordings. Video8 equipment cannot play Hi8 recordings.
Both S-VHS and Hi8 retained the audio recording systems of their base formats; VHS HiFi Stereo outperformed Video8/Hi8 AFM, but remained restricted to high-end machines.
In the late 1980s, digital (PCM) audio was introduced into some higher grade models of Hi8 (and SVHS) recorders. Hi8 PCM audio operated at a sampling rate of 32 kHz with 12-bit samples — far short of CD-audio or SVHS PCM quality. PCM-capable Hi8 and SVHS recorders could simultaneously record PCM stereo in addition to the legacy (analog AFM) stereo audiotracks.
The final upgrade to the Video8 format came in 1998, when Sony introduced XR capability (extended resolution). Video8-XR and Hi8-XR offered a modest 10% improvement in luminance detail, while retaining full backward compatibility with older non-XR equipment. XR recordings were fully playable on older non-XR equipment, though without the benefits of XR.
Hitachi Digital8 Camcorder
Introduced in 1999, Digital8 is digital video recorded on Hi8 media using the industry standard DV codec. In engineering terms, Digital8 and miniDV are indistinguishable at the logical format level. Digital8 uses the same cassettes as Video8, but otherwise bears no resemblance to the Video8 analog video system. Some Digital8 equipment can play (not record) Hi8/Video8 recordings, but this is not a standard feature of Digital8 technology. To store the digitally-encoded audio/video on a standard NTSC Video8 cassette, the tape must be run at double the Hi8 speed. Thus a 120 minute NTSC Hi8 tape yields 60 minutes of Digital8 video. Most Digital8 units offer an ‘LP’ mode, which increases recording time on a NTSC T-120 tape to 120/2 * 1.5 == 90 minutes.
For PAL, the Digital8 recorder runs one-and-a-half times faster, thus a 120-minute PAL Hi8 tape yields 90 minutes of Digital8 video. PAL LP mode returns the tape speed to the Hi8 SP speed, so a Hi8 120 minute tape yields 120 minutes of Digital8 video.
Sony has licensed Digital8 technology to at least 1 other firm (Hitachi) who marketed a few models for a while, but presently, only Sony sells Digital8 consumer equipment. Digital8’s main rival is the consumer miniDV format, which uses narrower tape and a correspondingly smaller cassette shell. Since both technologies share the same logical audio/video format, Digital8 can theoretically equal miniDV in A/V performance. But as of 2005, Digital8 has been relegated to the entry-level camcorder market, where price and not performance is the driving factor. Meanwhile, miniDV is the de facto standard of the digital camcorder market, with DVD recordable camcorders also increasing in popularity due to the ability to take the media from the camcorder straight to a standard DVD player.
Tape and recording protection
As with many other video cassette formats, 8 mm videocassettes have a tape-protecting mechanism built into the shell. Unlike the ones on VHS and VHS-C shells, which consist of only a singular piece of plastic that protects the part of the tape that is read by the player/recorder, Hi-8’s tape protection mechanism consists of two pieces of plastic at the top of the shell that come together and form a casing that protects both sides of the tape, and a latch that prevents this casing from opening and exposing the tape. The playback/recording unit can depress this latch to open the casing and gain access to the tape.
To prevent the recording on the tape from being erased, there is a small “write-protect” tab that can be moved to one of two positions, labeled “REC” and “SAVE”, respectively. The tape can only be recorded on (or recorded over) when this tab is in the “REC” position. This is an improved version of the VHS write-protect tab, which prevents erasure after it has been (permanently) broken off.
Video8 outside the camcorder market
Efforts were made to expand Video8 from the camcorder market into mainstream home video. But as a replacement for full-size VCRs, Video8 failed. It lacked the long (5+ hour) recording time of both VHS and Betamax, offered no clear audio/video improvement, and cost more than equivalent full-size VCRs. Quite simply, there was no compelling reason to switch to Video8 for the home VCR application.
Initially, many movies were prerecorded in 8 mm format for home and rental use. The rental market for Video8 never materialized. Sony maintained a line of Video8 home VCRs well into the 1990s, but unlike VHS, 8 mm VCRs with timers were very expensive.
Sony also produced a line of video 8 mm Walkman-branded players and recorders with and without a flip up screen meant for video playback and limited recording. These have been adapted for digital 8 mm as well as miniDV formats even as portable DVD players have become popular in this application. Such players saw use in professional applications, particularly with airlines who, during the 1980s, adopted 8 mm as the format for in-flight movies. As of 2008, they remain in use on many airliners.
Among home and amateur videographers Video8/Hi8 was popular enough for Sony to make equipment for video-editing and production. The format also saw some use in the professional ENG/EFP field.
As of early 2007, the analog 8 mm formats are nearing the end of the road. Standard Video8 is already extinct in the new camcorder market. Hi8 (along with VHS-C) is still used for some entry-level camcorders aimed at consumers, but elsewhere has been almost entirely superseded by digital formats, such as its successor Digital8, miniDV, and miniDVD. However, both standard Video8 and Hi8 videocassettes remain widely and inexpensively available.
Some have questioned the future of Digital8, citing the fact that (as of early 2007) only Sony supported the format in the face of competition from MiniDV, and only in their entry-level camcorders. As of early September 2007, Sony’s last Digital8 camcorder, the DCR-TRV280, has been removed from their consumer lineup. (As of October 2007, the camera is still listed under their “business-to-business” section of their website.) Only two Digital8 devices now remain, both Digital8 video Walkmans. Sony has announced no plans for future models; it seems that we’ve probably seen the last of Digital8 camcorders, aside from remaining dealer stock and the used market, such as eBay.
In Video8 and its successors, the smaller head drum and tape left recorders more susceptible to the effects of ‘tape dropout’, where magnetic-particles are eroded from the tape surface. As the audio/video signal is held in a smaller area on a Video8 tape, a single dropout has a more damaging effect. Hence, dropout compensation in Video8 systems tend to be more advanced to mitigate the format’s vulnerability to dropouts. In this respect, VHS and Betamax’s larger head drums prove advantageous.
8 mm tapes should be stored vertically out of direct sunlight, in a dry, cool dust-free environment. As with any media, they will eventually deteriorate and lose their recorded contents over time, resulting in a build up of image noise and dropouts. Tapes older than 15 years may start to show signs of degradation. Amongst other problems, they can become sticky and jam playback units or become brittle and snap. Such problems will normally require professional attention.
However, the 8 mm format is no more prone to this than any other format. In fact, the metal particle technology used with the Video8 formats is more durable than the metal evaporated type used with MiniDV. Hi8 tapes can be either of Metal Particle (MP) or Metal Evaporated (ME) formulation.
Because 8 mm tapes use a metal formulation, they are harder to erase than the oxide tapes used with VHS, SVHS and Betamax tapes. As such, carefully stored, they are less susceptible to magnetic fields than the older formats.
Because Video8 and Hi8 are analog video formats, transferring either to computer requires digitization. One method is to feed the video signal to an analog capture card connected to the computer itself.
Another option involves the use of a pass-through adapter which outputs a digitized video signal in the industry standard DV format. Many consumer-level miniDV and Digital8 camcorders have this facility built-in. The DV signal can then be fed into a computer equipped with a firewire port.
A third route is to find a Digital8 camcorder which supports legacy playback of Video8 and Hi8, and which will output a digitized DV signal directly via its firewire port. This will usually yield an improved image quality compared to the previously mentioned methods, and can offer the advantage of direct computer control over the tape transport, which is difficult (may require extra hardware) or impossible for the bridge method mentioned above.
Once on a computer, footage can be edited, processed and transferred to DVD, the Internet, or back to tape.